1. Field of the Invention
The present invention relates to a measuring head, and in particular, to the measuring head comprising a damper apparatus which absorbs an impact and a vibration of a contact, used for a machine control gauge or a surface roughness profile shape measuring machine and so on mounted on a grinding machine and so on.
2. Description of the Related Art
As for a machine control gauge (automatic sizing device) or a surface roughness profile shape measuring machine and so on mounted on a grinding machine and so on, there is a measuring head used thereon. The measuring head comprises a seesaw member having a contact at its end and rotatably supported by a fulcrum member as its supporting point, an urging member which urges the seesaw member in one direction, and a detector provided on an opposite side to the contact with the fulcrum member in between, which detects a displacement of the contact by detecting the displacement of the seesaw member.
The detector uses a linear voltage differential transformer (commonly called differential transformer) called an LVDT (Linear Voltage Differential Transducer) comprised of a differential coil portion fixed on a measuring head proper and a core mounted on the seesaw member and inserted into the differential coil portion. A travel distance of the contact is detected as a change in voltage by the LVDT, and this value detected by the LVDT is processed by a control portion and acquired as the travel distance.
The machine control gauge is comprised of one seesaw member, and uses an L-shaped measuring head which measures the displacement at one location with one contact and a sandwiching type measuring head having two seesaw members built in as a pair and sandwiching a measured object with two opposed contacts to measure an outside diameter thereof.
The measuring head used for the machine control gauge, surface roughness profile shape measuring machine and so on has a viscous fluid such as silicone oil encapsulated therein and gives a damping force to movement of the contact in order to keep a measured value from becoming unstable due to measurement of a surface of discontinuity, surface roughness of a measuring plane, vibrations from the outside, an impact of the contact on contacting the measured object and so on.
For this reason, there are problems such as difficulty in adjustment and maintenance of the inside of the measuring head, being unable to incorporate a sensor using light such as a scale inside it, necessity of a closed structure of the entire measuring head and difficulty in adjustment of the damping force.
To solve these problems, there is a known measuring head which has an oil damper built in between the measuring head proper and the seesaw member (refer to Japanese Patent Application Publication No. 53-76483 for instance).